a phrase used to indicate that we refuse to defend a claim we've made---in other words, that we refuse to offer reasons that what we've said is true

PERSON-A: "You shouldn't hang out with her anymore."
PERSON-B: "After all she's done to help me? Wouldn't that be pretty mean and selfish of me?"
PERSON-A: "I'm *just saying*, you should quit hanging out with her."